BGA semiconductor device using insulating film

ABSTRACT

The present invention relates to a BGA semiconductor device using an insulating film. The BGA semiconductor device using the insulating film has purge holes (a) made between through-holes  2  in a base film  1  as a substrate, so that stagnant air is purged from voids (s) formed between the insulating film  4  set on the upper face of a wiring pattern  3  and the wiring pattern  3  via the purge holes (a) before electronic elements formed with chip bonding are packaged with a sealing resin  5.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a BGA semiconductor device using an insulating film.

[0003] 2. Description of Related Art

[0004] Conventional technology involves using an insulating film. Namely, a commonly used substrate is a base film in which through-holes are made, wiring is printed on the upper face thereof, the insulating film is set on the printed wiring, and a chip is placed on the upper face of the insulating film to provide for gold-streak bonding between the chip and the wiring. These electronic elements are packaged with a resin. Solder balls are welded to the through-holes at the reverse side of the base film. A BGA semiconductor device is manufactured in these procedures.

OBJECTS OF THE PRESENT INVENTION

[0005] Unfortunately, when the wiring is printed on the base film and the insulating film is further set on the upper face thereof, an unevenness is formed on the insulating film in conjunction with the printing of the wiring pattern, creating gaps between wires and between the wiring and the insulating film covering the upper face thereof, where air stays. If the electronic elements are packaged with the resin under such circumstances, air staying in the gaps expands, whereby portions of the base film are blistered to give height inequality to the lower end faces of a number of solder balls welded to the reverse side of the base film. Using the BGA semiconductor device in such conditions precludes the accurate connection of another terminal to the solder balls located at the reverse side of the BGA semiconductor device and the satisfactory function of a semiconductor.

[0006] It is an object of the present invention to provide a BGA semiconductor device in order to overcome these defects.

SUMMARY OF THE INVENTION

[0007] According to one aspect of the present invention, a BGA semiconductor device using an insulating film comprises purging air staying between an insulating film and a base film via purge holes formed between through-holes in the base film.

[0008] According to another aspect of the present invention, the BGA semiconductor device using the insulating film, wherein a wiring pattern is printed on the upper face of the base film in which the through-holes are made, the insulating film is set on the wiring pattern, a chip is placed on the upper face of the insulating film to provide for gold-streak bonding between the chip and the wiring, and these electronic elements are packaged with a resin, while solder balls are welded to the through-holes at the reverse side of the base film, comprises purge holes made between the through-holes in the base film, so that air staying in recessed portions formed between the insulating film set on the upper face of the wiring pattern and the wiring pattern is purged via the purge holes.

BEST MODES FOR CARRYING OUT THE INVENTION

[0009] According to the present invention, the purge holes located between through-holes are independently made during the formation of the base film, the wiring pattern is printed on the base film, and the insulating film is further set on the upper face thereof.

[0010] In such a state, air purge via the purge holes is carried out, whereupon stagnant air is purged from voids formed between each wire-to-wire recessed portion of the wiring pattern and the insulating film set on the upper face thereof until the voids between the base film and the insulating film are cleared out.

[0011] If these electronic elements are molded and packaged with the resin under such circumstances, stagnant air completely disappears in the hardened resin. This eliminates the possibility of expansion of air in the molded resin due to heat during molding or heat generated around the BGA semiconductor device, when used. Therefore, non-continuity with connection terminals during using the BGA semiconductor device, due to the non-uniform terminal faces of the solder balls welded to the through-holes in the base film, is prevented.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an explanatory sectional view of a BGA semiconductor device using an insulating film.

[0013]FIG. 2 is a plan view of a base film used for the BGA semiconductor device using the insulating film.

[0014]FIG. 3 is an enlarged sectional view along a line I-I shown in FIG. 2.

[0015]FIG. 4 is an explanatory sectional view showing the condition of air purge in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Referring to the drawings, the embodiments of the invention are detailed.

[0017]FIG. 1 shows a sectional view of a BGA semiconductor device A of the present invention, where a base film 1 as a substrate contains a number of through-holes 2 to which terminals composed of solder balls are welded, the upper face of the base film 1 is provided with a printed wiring pattern 3 and the upper face of the wiring pattern 3 is provided with a set insulating film 4 of polyimide. The upper face of the insulating film 4 is bonding-covered with a chip 7.

[0018] Further, purge holes (a) are made between through-holes 2 in the base film 1, as shown in an enlarged sectional view of FIG. 3, and the purge holes (a) is put in communication with voids (s) to be formed between the base film 1 and the insulating film 4. Namely, since recessed portions spaced from each other as predetermined are formed between wires of the wiring pattern 3 printed on the upper face of the base film 1, the voids (s) are formed between each wire-to-wire recessed portion of the wiring pattern 3 and the insulating film 4 covering the upper face thereof. The certain voids (s) formed between each wire-to-wire recessed portion of the wiring pattern 3 and the insulating film 4 covering the upper face thereof cause the existance of stagnant air. With the purge of the stagnant air from the voids (s) formed by the wire-to-wire recessed portions via the purge holes (a) opening in the base film 1 by using a vacuum, the voids (s) formed between each wire-to-wire recessed portion and the insulating film 4 are cleared out to eliminate the existance of the stagnant air. Under such circumstances, bonding of a chip and molding and packaging of the electronic elements with a resin 5 are carried out.

[0019] Then, the solder balls 6 are transferred via a flux to the through-holes 2 at the reverse side of the base film 1 and welded to the through-holes 2 in a reflow process.

[0020] The processes of manufacturing the BGA semiconductor device of the present invention, which is constructed in the above-described procedures, are described below, including the purge of stagnant air between the wiring pattern 3 and the insulating film 4. First, the purge holes (a) are made between the through-holes 2 in concurrence with the formation of the through-holes 2 in the process of producing the base film 1.

[0021] The purge holes (a) each of which has a diameter equal to or smaller than the diameter of each through-hole 2 are located nearly midway between the through-holes 2.

[0022] Thus, the through-holes 2 are positioned to have continuity with the printed wires when the wiring pattern 3 is printed in the following process, the voids (s) requiring air purge are formed between the through-holes 2 in coating the upper face thereof with the insulating film 4 and the purge holes (a) communicate with the voids (s).

[0023] The purge holes (a), if located midway between the printed wires, communicate with the voids (s) to be formed by the insulating film 4 in the following process.

[0024] When the insulating film 4 of polyimide is set on the upper face of the wiring pattern 3, the certain voids (s) are formed between each wire-to-wire recessed portion of the wiring pattern 3 and the insulating film 4. The voids (s) are made open to the atmosphere in communication with the purge holes (a) formed between the through-holes 2.

[0025] To achieve air purge from the voids (s), the electronic elements including the base film 1, the wiring pattern 3 and the insulating film 4 set on the upper face thereof are stored in a vacuum chamber and the vacuum chamber is evacuated by using a vacuum.

[0026] The result is air purged from the voids (s) via the purge holes (a).

[0027] Complete air purge brings the insulating film 4 in close contact with the wire-to-wire recessed portions of the wiring pattern 3 and eliminates the possibility of reentering air into the recessed portions because of complete disappearance of the voids (s).

[0028] It is acceptable to provide means for blocking the purge holes (a) after air purge, for example, means for applying a blocking paint to the opening ends of the purge holes (a), if necessary.

[0029] After air purge, the chip 7 is placed on the electronic elements for bonding of gold streaks 8 between the chip and the wiring in a chip bonding process.

[0030] Then, the electronic elements are molded and packaged with the resin 5.

[0031] The solder balls 6 are put in the through-holes 2 at the reverse side of the base film 1 and welded thereto in the reflow process. The BGA semiconductor device A manufactured in these processes is formed with no existance of air in the package, therefore eliminating the possibility of expansion of air in the semiconductor device due to heat.

[0032] This prevents the warping of the base film due to heat generated in the reflow process or during using the semiconductor and gives height equality to the lower end faces of the plurality of solder balls to ensure connection between each solder ball and another terminal during using the semiconductor.

[0033] Additionally, there is no cracking to the package due to thermal expansion of air.

EFFECTS OF THE INVENTION

[0034] According to the present invention, the purge holes are made between the base film and the through-holes so that air staying in the recessed portions formed between the insulating film set on the upper face of the wiring pattern and the wiring pattern is purged via the purge holes, therefore eliminating the existance of stagnant air between the base film and the insulating film and preventing poor continuity between terminals during using the semiconductor as a result of thermal expansion of air during molding the electronic elements with the resin which causes the base film to be blistered to give height inequality to the lower end faces of the solder balls. 

What is claimed is:
 1. A BGA semiconductor device using an insulating film comprises purging air staying between said insulating film and a base film via purge holes formed between through-holes in said base film.
 2. A BGA semiconductor device using an insulating film, wherein a wiring pattern is printed on the upper face of a base film in which through-holes are made, said insulating film is set on said wiring pattern, a chip is placed on the upper face of said insulating film to provide for gold-streak bonding between said chip and wiring, and these electronic elements are packaged with a resin, while solder balls are welded to said through-holes at the reverse side of said base film, comprises purge holes made between said through-holes in said base film, so that air staying in recessed portions formed between said insulating film set on the upper face of said wiring pattern and said wiring pattern is purged via said purge holes. 